Method of impregnating lubricant into abrasive wheels



United States Patent 3,321,287 METHOD OF IMPREGNATING LUBRICANT INTO ABRASIVE WIEELS Jesse F. Hunsberger, Pottstown, and Donald J. Tucker,

Huntingdon Valley, Pa., assiguors to A. 'P. de Sanno & Son, Inc, Phoenixville, Pa., a corporation of Pennsylvania No Drawing. Filed July 20, 1964, Ser. No. 383,926

1 Claim. (Cl. 51- 295) The present invention relates to abrasive grinding wheels and other abrasive tools containing a solid lubricant and to'methods for increasing the permanence of the retention of solid lubricant therein.

A purpose of the invention is to permanently retain in the pores of an abrasive tool, such as a'grinding Wheel, a solid lubricant such as graphite, :by introducing with, or after, the introduction of the solid lubricant a resinous bonding material for retaining the lubricant.

A further purpose is to impregnate an abrasive wheel such as an abrasive grinding wheel, with a solid lubricant in a suitable medium, and to introduce with, or after, the introduction of the solid lubricant, a resinous bond which will hold the solid lubricant in the pores of the tool.

A further purpose is tointroduce a solid lubricant with aresinous bond in making an abrasive wheel, the resinous bond retaining the solid lubricant in place in the pores of the wheel.

Further purposes appear in the specification and in the claim.

It has been found in the prior art that certain materials can be introduced into the pores of abrasive tools such as grinding wheels, and cause the tool to run cool. They function in addition to a liquid coolant such as water, an alkaline solution, an oil, or an oil emulsion.

A reason for this extraordinary property is not fully understood, but the fact is well established.

Typical of the most widely used of these solid lubricants is graphite. To some extent, as later explained, the chlorinated napthalenes which are of waxy consistency, such. as tetra-, pentaand hexachloronaphthalene, possess the properties of solid lubricants.

Difliculty has been encountered with graphite in that it is washed out of the pores of the wheel by the liquid coolants during service, and therefore the effectiveness of the wheel is greatly reduced after a period of service.

We have discovered that it is possible to introduce a solid lubricant such as graphite and to retain this material permanently in the abrasive wheel by introducing a resin ous bond. We also have discovered that the resinous bond does not impair the functioning of the solid lubricant, but leaves it in a form which is capable of effectively cooling the wheel.

The invention, while primarily intended to be used with vitrified bonded abrasive wheels, can be applied equally well to abrasive wheels and other tools having one of the other usual types of bond, such as resinous bonded, shellac bonded, magnesium oxychloride bonded, sodium silicate bonded, and rubber bondedwheels.

The resinous :bond can be introduced with the solid lubricant or after introducing the solid coolant. The solid lubricant can also be introduced with the bond which forms the wheel itself if no high temperature is involved in forming the bond which would destroy the resinous bond. The resinous bond is, where possible, cured in place.

EXAMPLE 1 For convenience is comparing the properties of the different wheels, the various examples employ aluminum oxide abrasive grit of 36 mesh size.

In this example a vitrified bonded abrasive wheel was bonded with a conventional vitrified bond consisting of 3,321,287 Patented May 23, 1967 clays, feldspars and hits totalling 14% based on the weight of the wheel. The wheel was molded using conventional vitrified bonding molding technique and was then fired at a temperature of 2280 F.

After the wheel had cooled,-it was treated by dipping in a dispersion of graphite lubricant and resinous bond as follows:

Percent Dispersion of graphite powder 7% in isopropyl I alcohol Liquid A stage phenol-formaldehyde resin 15 The graphite powder was obtained according to the teaching of J. L. King, U.S. Patent 2,986,519, granted May 31, 1961, for Process of Forming a Graphite Lubricant. v

The A stage phenol-formaldehyde resin had the following characteristics:

. Monsanto 482 Solids content 66 to 71% by weight. Viscosity 335-385 cps. at 25 C. Polymerization test for dry rubber at 150 C. SDP-509-l 100 seconds minimum. Specific gravity at 25 C 1.l1.200. Water content 4% maximum. Free formaldehyde content 1.5% maximum. pH 5.7 to 6.2.

The dispersion of graphite and A stage phenol-formaldehyde resin was placed in a vessel and vitrified bonded abrasive wheels were submerged in the solution for a few minutes until all bubbling ceased.

The wheels were then removed from the solution and allowed to drain. Where the wheels were of large diameter they were rotated at low speed, approximately 1000 r.p.m., to insure good distribution of the lubricant and carrier throughout the wheels to insure homogeneity. This is done with wheels which are of .six inches in diameter or larger.

After drying, the Wheels'were cured in an oven at 220 F. for two hours and at 350 Fffor two additional hours. a The wheels were found to grind effectively and remain cool, and the lubricant remained in place throughout the service of the wheels. I

EXAMPLE 2 In this example grinding wheels of the same character were used. Instead of 15% of phenol-formaldehyde liquid resin, in this case 15% of an epoxy liquid resin formulation consistingof the following was employed:

Percent Liquid epoxy resin condensation product of his phenol-A and epichlorohydrin 66% Polyamide activator 33 /3 The liquid epoxy resin condensation product of his phenol-A and epichlorohydrin is made according to U.S.

Patent 2,705,223 assigned to General Mills. The liquid resin has the following characteristics.

Specific gravity 1.17 at 23 C.

Viscisity 13,000 cps. at 23 C.

Epoxy value 0.523 equivalents per gram. Flash point 249 C.

Reaction 1 Bisphenol A Epichlorohydrin Reaction 2 shows the production of the polyamide activator used in Example 2. 9, 2 linoleic acid and 9, 11 linoleic acid (isomerized) are reacted according to well known practice to form linoleic acid dimer.

As shown in Reaction 3, linoleic acid dimer reacts with a diamine such as ethylene diamine, also according to well known practice to form the polyamide activator referred to in Example 2. The properties of the polyamide activator are as follows:

Amine value 290 to 320.

Condition of fluid:

Viscosity 80 to 120 poises at 40 C. Specific gravity 0.97.

In manufacturing the polyamide activator the ingredients are blended in an autoclave at low temperature and the temperature is gradually raised high enough so that water distills 01f from the reaction at a rate which maintains the temperature near 100 C. When distillation becomes negligible, temperature is raised from 150 to 250 C. and vacuum is applied. Reaction can be carried on in xylenol as a solvent.

The following US. patents of General Mills describe the production of the polyamide: 2,379,413 and 2,705,223.

Reaction 2 coon H (I OH (IJQOH j (C 1 r (I: (Cll zh I HM H CH CH CH ll I CH HC CH-(CH2):-COOH CH: l H

I CH HC CH-CHrCH=CH(CH2)4-CH; CH ll g 1] CH C OH (CH2)! (CH2); 2); I

l CH3 CH3 CH3 9,2 Linolelc 9,11 Linolelc Linoleic acid acid acid dimer (isomerized) Reaction 3 1TH: i Llnoleie acid dimer(l3Ha NHg l? i t C-NCH2CH2NR Ethylene diamine((|]H2)7 H l H(I'IJ CH(CHz)7-CNCH2CH2NR HC\ CHCHzCH=CH-(CH2)4CHa Where R =11 or another linoleic dimer Reaction 4 shows the reaction between the liquid epoxy resin condensation product and the polyamide activator in Example 2. In Reaction 4, R is an alkyl group, straight or branched, or an unsaturated alkylene, straight or branched carbon chain having one to fifteen carbon atoms. R is as shown in Reaction 1, in which n may vary from zero to fifteen and the molecular Weight may vary between and 5000.

In this case the graphite dispersion was dispersed in a solvent mixture of 40% of methylethylketone, 20% of isopropyl alcohol and 40% of toluene by volume.

The procedure of Example 1 was followed, except that the wheels after impregnation were cured at a temperature of about 250 F. for a time of one to two hours.

It was found that the lubricant functioned effectively and remained in place in the wheels.

EXAMPLE 3 The procedure of Example 1 was followed, except that instead of 15% of phenol-formaldehyde A stage liquid resin, 15% of polyurethane liquid resin was used having the following composition:

100 parts by Weight of polyurethane prepolymer. 10 parts by weight of polyol, in this case triisopropanol- V amine.

Reaction 5 shows the general reaction between an isocyanate and an alcohol to form urethane. In Reaction 5, the isocyanate can be toluene diisocyanate, hexamethylene diisocyanate, di-phenylmethane diisocyanate, the dimethyl derivative thereof, 1,5-naphthalene diisocyanate, triphenyl methane triisocyanate, xenylene diisocyanate, or the dimethyl derivative thereof, or chlorophenyl-3-4-diisocyanate. In Reaction 5 R may be hydrogen or an alkyl group having from 1 to 35 carbon atoms in the carbon chain, or a similar alkylene group, or a corresponding hydroxylated group.

Reaction 6 shows the general reaction for forming a urethane polymer. In Reaction 6 R will correspond to any of the isocyanates referred to in Reaction 5. R in Reaction 6 will correspond to any of the groups which constituted R in Reaction 5.

Reaction 7 shows a general reaction for producing a polyurethane prepolymer by reacting toluene diisocyanate with a polyol. In Reaction 7 and also Reaction 8, R may be any alkyl group having from 1 to35 carbon atoms or a corresponding unsaturated or alkylene group or a substituent thereof substituted, for example, by hy- Reaction 5 II RNCO HOB Rl I-COR Isocyanate Alcohol Urethane Reaction 6 nOCN-RNCO nHOR-OH H[ORO O CHN-R/Lv-NC O Urethane polymer Reaction 7 20H: NCO HOR-OH Toluene diisocyanate Polyol O O C C N N Prepolymer Reaction 8 OCN Q OH 1 C l E E i 0 ON Reaction 8 shows the general reaction which takes place when a polyurethane prepolymer reacts with a phenol-formaldehyde resin.

The particular polyurethane prepolymer used is sold commercially by Isocyanate Products, of Wilmington, Delaware, as Castomer S 10. It is made by reacting toluene diisocyanate with castor oil, there being at least one mol of diisocyanate for each hydroxyl group.

The polyurethane prepolymer is produced by reacting 1300 grams of toluene diisocyanate and 1800 grams of castor oil, reaction being continued until the temperature rises to 181 F. and then the temperature being raised to 275 F. for one hour.

The polyurethane prepolymer has the following properties:

Specific gravity 1.073 Percent of NCO 10.6 Equivalent weight 396 The solvent used, instead of isopropyl alcohol was methylisobutylketone. Alcohols are counter-indicated in this case, as they are reactive with polyurethanes.

After impregnation the wheels were cured at 250 F. for one hour. The solid lubricant functioned properly and was effectively bonded in place.

EXAMPLE 4 The procedure of Example 1 is carried out, except that the dispersion in which the wheels were dipped consists of the following:

Percent Dispersion of graphite powder 7% in isopropyl alcohol 50 Solution of equal weight parts of pentaand hexachloronaphthalene 25% in toluene 50 After impregnation and draining the Wheels are heated in an oven for two hours at 200 F.

It is found in this case that the chlorinated naphthalene imparts supplemental cooling functions and also effectively retains graphite in the pores of the wheel. Other chlorinated naphthalenes in the range between trichlorand hexa-chlor can be used with success.

EXAMPLE 5 Following the general procedure of Example 1, the wheels are impregnated with a dispersion of 7% graphite dispersed in isopropyl alcohol, then drained and oven dried at 200 F. for two hours.

Subsequently the wheels are impregnated with a solution of 15% A stage phenol-formaldehyde liquid resin as in Example 1 in of a solvent such as isopropyl alcohol, and then drained and cured as in Example 1; It is found that the results obtained are comparable to that produced in Example 1. In all of Examples 2 to 4 the resinous bond can be added as a separate step after the impregnation with the dry lubricant such as graphite.

EXAMPLE 6 In this case chlorinated naphthalene was used in place of other resinous bond. The following solution was used for impregnating the wheels as in Example 1:

Grams Dispersion of 7% graphite in isopropyl alcohol 25% of equal parts of pentaand hexa-chloronaphthalene in toluene 25 The wheels after impregnating and draining are placed in an oven at 200 F. for two hours.

In all of the above examples, the wheels may be impregnated two, three, or four times as desired. A wheel impregnated according to one of the examples can be impregnated the next time according to another example, as desired.

EXAMPLE 7 In this example the solid coolant and the bond were incorporated in the process of manufacturing the wheel, which had a resinous bond. The composition was as follows:

Grams Aluminum oxide abrasive through 36 mesh 750 Powdered B stage phenol-formaldehyde resin 205 A liquid resinous mixture consisting of equal parts by weight of a dispersion of graphite 7% in isopropyl alcohol and liquid A stage phenol-formaldehyde resin 112 In producing the wheel the granular abrasive was mixed with the liquid resinous mixture, and some of the solvent was allowed to evaporate during the mixing. Then the powdered phenol-formaldehyde resin was added and thoroughly mixed with the ingredients. The wheel was then molded and cured in an oven at 325 F. for 27 to 42 hours, in this case 27 hours.

It is found that the solid lubricant Was effective and was retained in place.

EXAMPLE 8 In this case the graphite is incorporated on the abrasive grain itself before making the wheel. The abrasive grain is mixed with a dispersion of graphite 7% in isopropropyl alcohol and the solvent is allowed to evaporate, coating the graphite on the abrasive grains. Then the grit is made into a resinous bonded wheel by typical technique of which the following is an example:

Percent Abrasive grain 75 Solid B stage phenol-formaldehyde resin powder 18.7 A stage phenol-formaldehyde liquid resin 6.3

The wheel is molded and cured suitably at 325 F. for 27 to 42 hours, in this case 27 hours.

Using grain coated with graphite, similarly any other type of wheel bonding, such as shellac, magnesium oxychloride, sodium silicate, or rubber, can be applied.

The abrasive grains employed may be of any suitable character, whether natural or synthetic. Among the natural abrasive grains which can be used are corundum, emery or sand. Among the synthetic abrasive grains which will be used are aluminum oxide, silicon carbide, zirconium spinel, titanium spinel, various metal nitrides, and diamonds.

In experimental work using wheels produced according to the invention, it is found that various advantages exist. The wheel has 25% more life before dressing and retains this characteristic indefinitely.

The wheel increases the number of pieces ground by about 25% and this continues throughout the life of the wheel.

The metal finish obtained is 50% better and this remains as a characteristic of the wheel.

There is less loading of metal particles in the wheel.

The over-all wheel life is increased.

The tendency to form heat checks on the work pieces is greatly reduced.

The quantity of solid lubricant such as graphite on the weight of the Wheel will vary in various embodiments from 0.25% to 10%. I

The quantity of liquid resin for bonding the solid lubricant will vary from about to 50% of the weight of the solid lubricant suspension.

Where the solid lubricant is put in prior to or along with the resin, or other bonding agent, for making up the abrasive wheel, the wheel bonding materials will constitute between 5 and 40% of the Weight of the abrasive wheel.

All percentages relating to compositions stated herein are by weight unless otherwise indicated.

Mesh size is expressed in Tyler standard mesh per linear inch.

In view of our invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art to obtain all or part of the benefits of our invention without copying the method and article of manufacture as shown, and we therefore claim all such insofar as they fall within the reasonable spirit and scope of our claim.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

The process of improving the cooling capability of a vitrified bonded abrasive wheel which comprises the steps of preparing a'dispersion of graphite powder in isoproply alcohol wherein the graphite forms about 7%, of the dispersion, forming a mixture of the dispersion of graphite powder and isopropyl alcohol with a liquid phenol-formaldehyde resin wherein the phenol-formaldehyde resin comprises about 15% of the mixture, dipping the vitrifiedbonded abrasive Wheel into the mixture and impregnating the mixture within the pores of the wheel, removing the wheel from the mixture and allowing it to drain, and curing the mixture.

References Cited by the Examiner UNITED STATES PATENTS 1,310,360 7/1919 Martin 51-295 1,573,061 2/1926 Hartmann 51-295 2,050,992 8/ 1936 Aust 51-295 2,125,782 8/1938 Heald 51295 2,367,995 1/1945 Buckey 51295 2,862,806 12/1958 Nestor 51295 2,968,577 l/1961 Helling et a1. 51-295 3,062,633 11/ 1962 Coes 51295 ALEXANDER H. BRODMERKEL, Primary Examiner.

MORRIS LIEBMAN, Examiner.

D. I. ARNOLD, Assistant Examiner. 

